Certain types and sizes of mobile machines, e.g., large rubber-tired, off-highway construction loaders, agricultural tractors and the like, include frames or sections capable of limited movement with respect to one another. This capability makes the machine much more maneuverable. Such frames are connected by one or more hinges, sometimes called pivot joints, permitting such movement and machines so constructed are said to be "articulated." In the vernacular, they bend in the middle.
The frames or sections of such machines are at least capable of relative movement in a single plane as would occur when the machine is articulated on a flat surface. Such frames are also capable of oscillatory movement one with respect to the other; that is, the frames can "twist" to a limited extent with respect to one another. Such twisting motion occurs when the machine moves over undulating terrain.
Machines of the foregoing type frequently operate under dirty conditions. Airborne dust, mud particles, grain chaff and the like collect on the machine and one place where such contaminants accumulate is on oily, greasy surfaces including those of the pivot joints. As a consequence, such joints are prone to accelerated wear. The machine manufacturer typically provides an external grease fitting (sometimes called a "zerk" fitting) at such joints for periodic joint greasing by the machine operator using, e.g., a hand-operated grease gun. These grease fittings are very similar to those used to lubricate the chassis of an automobile.
Such conventional joint arrangements are characterized by at least two disadvantages. On is that for continuing joint lubrication and reasonable joint life (particularly in dirty operating environments--the usual case), the joint must be lubricated frequently, e.g., every ten hours or so of operation. Experience has demonstrated that many machine users simply fail to follow the manufacturer's instructions in this regard.
Another disadvantage is that the lubricant channels (through the zerk fitting and connecting passages into the joint) often become packed with a mixture of dirt and grease. Such mixture hardens and is difficult to remove--mere application of pressurized lubricant from a grease gun may well be insufficient to dislodge it. As a result, the machine operator may believe that s/he is effectively lubricating the joint when, in fact, no fresh lubricant is being introduced to the vital sliding friction surfaces. Premature joint wear and failure result.
An improved pivot joint lubrication device which accommodates oscillating and articulating movement, which is readily filled with lubricant and which lubricates vital pivot joint parts while obstructing entry of dust and dirt into the joint would be an important advance in the art.